Embodiments of the present disclosure generally relate to implantable medical devices, and more particularly to a system and method for controlling charging energy delivered to an implantable medical device.
Numerous medical devices exist today, including but not limited to electrocardiographs (“ECGs”), electroencephalographs (“EEGs”), squid magnetometers, implantable pacemakers, implantable cardioverter-defibrillators (“ICDs”), neurostimulators, electrophysiology (“EP”) mapping and radio frequency (“RE”) ablation systems, and the like. Implantable medical devices (hereafter generally “implantable medical devices” or “IMDs”) are configured to be implanted within patient anatomy and commonly employ one or more leads with electrodes that either receive or deliver voltage, current or other electromagnetic pulses (generally “energy”) from or to an organ or tissue (collectively hereafter “tissue”) for diagnostic or therapeutic purposes.
In order to provide consistent therapy and reliable operation, IMDs are often charged and re-charged to store energy within one or more batteries. Because the IMDs are implanted within patients, the IMDs are charged by an external charger that transmits energy into the IMDs, such as through radio frequency (RF) signals.
Each IMD is generally charged as quickly and safely as possible. However, if charging energy is input into the IMD too quickly, the temperature of the IMD may increase to dangerous levels and may cause tissue damage
During a charging process, energy from an external charger is input into the IMD. The IMD typically includes a pre-regulator that accepts the charging energy when the internal battery requires charging, but rejects the charging energy when the battery is charged to an acceptable or full level. Some of the charging energy available to the IMD is often wasted as heat, which may be caused by eddy currents in the metal can or case of the IMD. Any charging energy rejected by an IMD pre-regulator increases the heating in the case. As such, if the charging process occurs too fast, and/or if the IMD rejects the charging energy, the temperature of the IMD may quickly escalate. As such, the IMD may overheat.
Additionally, certain external chargers are battery-operated. Transmitting charging energy from an external charger typically drains the battery power. For example, during a typical charging process, the external charger transmits charging energy to an IMD, even when the IMD rejects the charging energy. Accordingly, even though the charging energy may not be accepted by the IMD, the charging energy is still being transmitted from the external charger, and thus depletes the battery of the external charger.